Electrosurgery is one form of a surgical cutting and coagulating procedure. Electrosurgery has two primary modes--monopolar and bipolar. Monopolar surgery uses an instrument, with a single electrode such as a single loop instrument, and a grounding pad as the means to administer the output of a surgical generator to the patient. In contrast, bipolar instruments include two electrodes in close proximity to each other. Typically, one electrode is a supply electrode and the other electrode is a return electrode. Bipolar instruments operate at much lower power levels than monopolar instruments and thus do not disturb nearby tissue. Examples of bipolar instruments are shown in U.S. Pat. Nos. 5,290,286 (Parins); 5,192,280 (Parins); 5,013,312 (Parins et al.); 5,282,799 (Rydell); 5,071,419 (Rydell) and WO 93/13719 (Fleenor et al.).
Wire electrodes, which are used in some such instruments, are generally rounded in cross-section and thus do not concentrate energy in any particular radial direction. Rounded electrodes also present a relatively large contact area to the surgical site. This may be undesirable if the area of interest is very small. Furthermore, it is difficult to make a wire electrode which has a very small diameter (i.e., width). The smaller the diameter, the smaller the cross-sectional area and the finer the electrode. Finer electrodes make finer cuts. An instrument with very fine electrodes can be used in tight crevices and in small areas, such as certain predefined regions of the brain. It is also a desirable goal for electrodes to have low resistance so that only a small amount of power need be applied to the electrodes to effectively cut and coagulate the desired tissue. By using less power at the surgical site, the device can be used in delicate surgical procedures, such as neurosurgery, with less risk of damaging neighboring areas.
Despite the variety of electrodes known in the prior art, there is still a need for a finer electrode which can also concentrate energy in the radial direction, is easy and inexpensive to fabricate, and has relatively low resistance. The present invention fills this need by providing an electrode tip with very fine electrodes that have sharp edges in cross-section and are preferably fabricated by photo chemical machining.